Apparatus and method for stylet-guided vertebral augmentation

ABSTRACT

A stylet-guided balloon vertebroplasty system, as well as methods for bone augmentation using same are provided. In certain embodiments, a pre-curved stylet with an overlying delivery tube may be used to target an approximately centered target site within a bone structure, facilitating direction thereto of an expandable member useful for creating a cavity that may receive curable material to restore bone height and/or to reinforce the bone structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 12/615,573, filed Nov. 10, 2009, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

Embodiments disclosed herein generally relate to systems and methods for stabilizing bone structures. More particularly, they relate to systems and methods for stabilizing, and restoring the height of, a bone structure, such as a vertebral body.

BACKGROUND

Surgical intervention of damaged or compromised bone sites has proven highly beneficial for patients, including, for example, patients with back pain associated with vertebral damage. The vertebral damage may be due to injury and/or a degenerative condition such as, for example, aging and/or osteoporosis.

Bones of the human skeletal system include mineralized tissue that may be generally categorized into two morphological groups: “cortical” bone and “cancellous” bone. Outer walls of all bones are composed of cortical bone, which is a dense, compact bone structure characterized by a microscopic porosity. Cancellous or “trabecular” bone forms the interior structure of bones. Cancellous bone is composed of a lattice of interconnected slender rods and plates known by the term “trabeculae”.

During certain bone-related procedures, cancellous bone is supplemented by an injection of a palliative (or curative) material employed to stabilize the trabeculae. For example, superior and inferior vertebrae in the spine may be beneficially stabilized by the injection of an appropriate, curable material (e.g., PMMA or other bone cement or bone curable material). In other procedures, percutaneous injection of stabilization material into vertebral compression factors, by, for example, transpedicular or parapedicular approaches, has proven beneficial in relieving pain and stabilizing damaged bone sites. Such techniques are commonly referred to as vertebroplasty.

A conventional vertebroplasty technique for delivering the bone stabilizing material entails placing a cannula with an internal trocar into the targeted delivery site. The cannula and trocar are used in conjunction to pierce the cutaneous layers of a patient above the hard tissue to be supplemented, then to penetrate the hard cortical bone of the vertebra, and finally to traverse into the softer, cancellous bone underlying the cortical bone. After the assembly is positioned in the cancellous bone, the trocar may be removed, leaving the cannula in the appropriate position for delivery of curable material that will reinforce and solidify the target site.

In some instances, an effectiveness of the procedure may be enhanced by forming a cavity or void within the cancellous bone, and then depositing the curable material in the cavity. For example, a balloon or other expandable device may be initially deployed and then expanded in a particular vertebroplasty procedure sometimes referred to as kyphoplasty. This action, in turn, compresses cancellous bone and other tissue to form a cavity, and may also cause a “height” of the bone to increase. As a point of reference, vertebroplasty is a common treatment for a fractured vertebral body, and the height of a fractured vertebral body is oftentimes significantly less than a native or natural height that existed before vertebral degeneration. It has been postulated that the height of a fractured vertebral body may be restored or elevated to a near-normal state when subjected to internal expansion via a balloon or other expandable member. The mechanics of height restoration in conjunction with vertebroplasty stabilization is currently unclear at best. For example, certain techniques may employ a bipedicular approach in which two balloons are inserted into the vertebral body and inflated, resulting in an increase in height (and the cavity or cavities described above).

There exists a need in the medical device field for improved systems and methods for restoring the height of, and stabilizing, a fractured vertebral body or other bone structure. In particular, it would be desirable to provide apparatus and methods to symmetrically provide bone augmentation that stabilizes a bone structure such as a vertebra, and that may also provide some height-restoration of said bone structure.

It may be desirable to provide a system and method that provides advantages with regard to reduced complexity and reduced procedure time while maintaining advantages of dual-balloon kyphoplasty and perhaps offering superior bone-centralization and symmetry of curable material placement.

BRIEF SUMMARY

In one aspect, embodiments disclosed herein may include a stylet-guided balloon vertebroplasty system, as well as methods for bone augmentation using same. In certain embodiments, a pre-curved stylet may be used to target an approximately centered target site within a bone structure, facilitating direction thereto of an expandable member useful for creating a cavity that may receive curable material to restore bone height and/or to reinforce the bone structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a curable material delivery and height restoration system, using apparatus for bipedicular access;

FIGS. 2A and 2B illustrate use of the system of FIG. 1 in performing a height restoration and curable material delivery procedure relative to a vertebra, with the vertebra being shown from a superior perspective;

FIG. 2C is a lateral view of the vertebral body of FIGS. 2A and 2B;

FIGS. 3A-3B illustrate the system of FIG. 1 in further performing the height restoration and curable material delivery procedures with a bipedicular dual-balloon method; and

FIGS. 4A-4H illustrate a system and method for transpedicular or parapedicular access providing stylet-guided, generally centralized location of a cavity/void and curable material placement therein.

DETAILED DESCRIPTION

Embodiments are described with reference to the drawings in which like elements generally are referred to by like numerals. The relationship and functioning of the various elements of the embodiments may better be understood by reference to the following detailed description. However, embodiments are not limited to those illustrated in the drawings. It should be understood that the drawings are not necessarily to scale, and in certain instances details may have been omitted that are not necessary for an understanding of embodiments disclosed herein, such as—for example—conventional fabrication and assembly.

Various embodiments will be described more fully hereinafter. The invention is defined by the claims, may be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey enabling disclosure to those skilled in the art. As used in this specification and the claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. The word “alternatively” and its variants are used inclusively rather than exclusively (i.e., “X, alternatively, Y” means “X and/or Y” rather than “only X or only Y”) unless otherwise apparent.

One embodiment of a curable material delivery and height restoration system 10 is shown in FIG. 1. The system 10 includes a first delivery assembly 12 a, a second delivery assembly 12 b, and at least one source of curable material 16. The delivery assemblies 12 a, 12 b may be substantially identical, and each includes a cannula device 18 a, 18 b and a cavity-forming device 20 a, 20 b. Details on the various components are provided below. In general terms, however, the cannula devices 18 a, 18 b each include an access cannula 22 a, 22 b for insertion into a bone site of interest in a patient. In the embodiment depicted in FIG. 1, the bone site of interest is a vertebra 30. After the access cannulas 22 a, 22 b are desirably located relative to the vertebra 30, a portion of each of the cavity-forming devices 20 a, 20 b are delivered to the vertebra 30 via the corresponding access cannula 22 a, 22 b, and operated to form cavities. The second cavity-forming device 20 b (alternatively the first cavity-forming device 20 a) may be removed, and the source of curable material 16 connected to the second cannula 22 b. In this regard, an delivery tube 14 may be employed, extending from the source 16 and through the second cannula 22 b.

Thereafter, the curable material source 16 is operated to deliver curable material to the cavity via the second cannula 22 b and/or the delivery tube 14. Subsequently, the first cavity-forming device 20 a may be removed and the curable material source 16 is connected to the first cannula 22 a (for example, via the delivery tube 14). The curable material source 16 is operated to deliver curable material into the corresponding cavity. With the approaches disclosed herein, the systems and methods disclosed herein will be able to provide for restore a height of the vertebra (or other bone site) 30 to a normal or near-normal state, and the delivered curable material will provide desirable stabilization.

The system 10 may be used for a number of different procedures including, for example, vertebroplasty and other bone augmentation procedures in which curable material is delivered to a site within bone, as well as possibly to remove or aspirate material from a site within bone. The system 10 is highly useful for delivering a curable material in the form of a bone curable material. The phrase “curable material” within the context of the substance that may be delivered by the systems and methods described herein is intended to refer to materials (e.g., composites, polymers, and the like) that have a fluid or flowable state or phase and a hardened, solid or cured state or phase.

Curable materials may include, but are not limited to, injectable bone cements (such as polymethylmethacrylate (PMMA) bone curable material), which have a flowable state wherein they may be delivered (e.g., injected) by a cannula to a site and subsequently cure into hardened, cured material. Other materials such as calcium phosphates, bone in-growth materials, antibiotics, proteins, etc., may be used in place of, or to augment bone cement (but do not affect an overriding characteristic of the resultant formulation having a flowable state and a hardened, solid, or cured state). This would allow the body to reabsorb the curable material and/or improve the clinical outcome based on the type of filler implant material. Although FIG. 1 illustrates a single source of curable material 16, in other embodiments, two (or more) sources may be provided. The sources may contain identical curable material compositions; alternatively, the compositions may differ (e.g., a first source may contain bone cement, while a second source contains a mixture of bone cement and bone in-growth material).

As mentioned above, the cannula devices 18 a, 18 b may be substantially identical, and each includes the outer/access cannula 22 a, 22 b. The cannula 22 a, 22 b is provided to be positioned in (or immediately proximate) the target or injection site for delivery of the corresponding cavity-forming device 20 a, 20 b, as well as curable material. The cannula 22 a, 22 b preferably is made of a surgical grade of stainless steel, but may be made of known equivalent material(s) that are both biocompatible and substantially non-compliant at the expected operating pressures. The cannulas 22 a, 22 b each define a proximal region 40 a, 40 b, a distal end 42 a, 42 b, and a lumen 44 a, 44 b (referenced generally), respectively, to allow various equipment such as the cavity-forming device 20 a, 20 b, a delivery tube 14, one or more stylets (not shown here, but discussed and illustrated with reference to embodiments of FIGS. 4A-4H below), and/or other elements, to pass therethrough.

Surrounding the proximal region 40 a, 40 b of the cannula 22 a, 22 b is an handle 46 a, 46 b for manipulating the cannula 22 a, 22 b and connecting the cannula 22 a, 22 b with one or more of the cavity-forming device 20 a, 20 b and/or the delivery tube 14. In some constructions, the cannula device 18 a, 18 b may further include a handle connector 48 a, 48 b serving as a proximal end of the corresponding cannula 22 a, 22 b. The handle connector 48 a, 48 b may simply be an extension of the cannula 22 a, 22 b. Alternatively, the handle connector 48 a, 48 b may incorporate features forming part of a locking mechanism component of the system 10. For example, the handle connector 48 a, 48 b may include a luer-lock type of connector, but other known connecting mechanism may be successfully interchanged (e.g., a conventional threaded hole, a threaded locking nut arrangement, etc.). Features of one suitable locking mechanism are described in U.S. Pat. No. 7,922,690, which is incorporated herein by reference in its entirety.

The cavity-forming devices 20 a, 20 b may be substantially identical and may assume various forms appropriate for forming a void or cavity within bone. In this regard, each of the cavity-forming devices 20 a, 20 b includes an elongated body 60 a, 60 b distally connected to or forming a working end 62 a, 62 b. The elongated body 60 a, 60 b is sized to be slidably inserted within the lumen 44 a, 44 b of the corresponding cannula 22 a, 22 b, and may include one or more tubes, shafts, etc., necessary for operation of the corresponding working end 62 a, 62 b. Thereafter, a proximal region 64 a, 64 b of the elongated body 60 a, 60 b may be connected to or form a cannula connector 66 a, 66 b. The cannula connector 66 a, 66 b may assume various forms conducive for selective, rigid attachment to the corresponding handle connector 48 a, 48 b as described above (e.g., the cannula connector 66 a, 66 b and the corresponding handle connector 48 a, 48 b collectively form a locking mechanism), and thus may include or contain a luer-lock threaded fitting. Alternatively, the cannula connector 66 a, 66 b may be omitted, and depth markings (not shown) included along an exterior of the proximal region 64 a, 64 b that facilitate desired locating of the working end 62 a, 62 b relative to the corresponding cannula 22 a, 22 b as described below.

The working end 62 a, 62 b may include one or more components appropriate for forming a cavity or void within bone. For example, in some constructions, the working end 62 a, 62 b may include one or more expandable or inflatable members (e.g., a single balloon, multiple balloons, a single balloon with two or more discernable inflation zones, etc.) constructed to transition between a contracted (e.g., deflated) state in which the working end/balloon 62 a, 62 b may be passed through the corresponding lumen 44 a, 44 b, and an expanded (e.g., inflated) state in which the working end/balloon 62 a, 62 b expands and compacts contacted cancellous bone. In this regard, a size and shape of the working end/balloon 62 a, 62 b may be predetermined and/or restrained with one or more additional components (not shown), such as internal and/or external restraints. In preferred embodiments the working end/balloon 62 a, 62 b will be structurally robust, able to withstand (e.g., not burst) at expected inflation pressures and when in contact with bone. Further, the first working end 62 a and the second working end 62 b may be identical or different.

The working ends/balloons 62 a, 62 b may be exteriorly coated with a material configured to resist bonding with the curable material being delivered to the vertebra 30. The anti-sticking coating may assume various forms as a function of the selected curable material, and in some embodiments is a silicone coating. Other materials exhibiting adversion to bonding with bone cement are also envisioned, for example, polypropylene. In related embodiments, a thin-walled expandable sleeve constructed of the selected anti-sticking material (e.g., a polypropylene sleeve) may be disposed over the working end/balloon 62 a, 62 b. Though not shown, one or both of the cavity-forming devices 20 a, 20 b may include a valve or similar component that operates to selectively seal the working end/balloon 62 a, 62 b.

The cavity-forming devices 20 a, 20 b each further include one or more additional components connected or operable through the proximal region 64 a, 64 b for actuating the corresponding working end 62 a, 62 b. By way of one non-limiting example, each of the cavity-forming devices 20 a, 20 b may include a source 68 a, 68 b of pressurized fluid (e.g., contrast medium) for inflating the balloon(s) carried or formed by the corresponding working end 62 a, 62 b. A hand-held, syringe-type pump may be used as the pressurized source. In other embodiments, a single one of the sources of pressurized fluid 68 a or 68 b may be provided and employed to inflate both of the working ends/balloons 62 a, 62 b individually. Appropriate balloon-inflation systems are well known and will readily be apparent to those of skill in the art.

Where provided, the delivery tube 14 is sized for insertion within the lumens 44 a, 44 b, and defines a distal tip 80 and a proximal section 82. As described below, the delivery tube 14 may be employed to deliver curable material to the target site. Thus, the delivery tube 14 has an outer diameter that is smaller than a diameter of the lumens 44 a, 44 b; however, the outer diameter of the delivery tube 14 preferably will not be so small as to allow curable material to readily travel around the outside of the delivery tube 14 and back into the corresponding cannula 22 a, 22 b.

A cannula connector 84 may be coupled to, or formed by, the proximal section 82 of the delivery tube 14. The cannula connector 84 is akin to the cannula connector 66 a, 66 b described above (e.g., combines with the selected handle connector 48 a, 48 b to form a locking mechanism), and thus may assume any of the forms previously described. Alternatively, the delivery tube 14, where provided, may form depth markings (not shown) along the proximal section 82 that facilitates desired locating of the distal tip 80 relative to the cannula 22 a, 22 b during use.

The delivery tube 14 is configured for fluid coupling to the curable material source 16. In some embodiments, a portion of the delivery tube 14 projects proximally beyond the cannula connector 84, and is fluidly coupled to the curable material source 16, for example via an injection connector 86. Alternatively, auxiliary tubing 88 may be provided with the curable material source 16, and fluidly connected to the delivery tube 14 via the cannula connector 84. In yet other embodiments, the delivery tube 14 is omitted, and the curable material source 16 connected directly to the handle connector/proximal end 48 a, 48 b (e.g., the auxiliary tube 88 is connected to the connector 48 a, 48 b; or the tubing 88 eliminated and the curable material source 16 (e.g., a syringe) directly coupled to the connector 48 a, 48 b).

The curable material source 16 may assume various forms appropriate for delivering the desired curable material, and may typically comprise a chamber filled with a volume of curable material and employing any suitable injection system or pumping mechanism to transmit curable material out of the chamber and through the delivery tube 14. Typically, a hand injection system is used where a user applies force by hand to an injector. The force is then translated into pressure on the curable material to flow out of the chamber. A motorized system may also be used to apply force.

Although the system 10 has been described as including the single source of curable material 16, in other constructions, a separate source of curable material 16 may be provided for each of the delivery assemblies 12 a, 12 b. Similarly, two (or more) of the delivery tubes 14 may be included. Along these same lines, the system 10 may be configured such that the curable material source 16 is directly connected to one or both of the cavity-forming devices 20 a, 20 b (e.g., the elongated body 60 a of the first cavity-forming device 20 a may form or terminate at a nozzle proximate (e.g., distal) the working end 62 a and through with the curable material may be directly dispensed).

The system 10 and other systems and methods disclosed herein will be useful in performing a wide variety of height restoration and bone stabilization procedures as part of an overall curable material delivery procedure. As such, FIGS. 2A-3B illustrate use of the system 10 in restoring the height of, and delivering curable material into, a target site of a vertebra 100. In general terms, the vertebra 100 includes pedicles 102 a, 102 b and a vertebral body 104 defining a vertebral wall 106 surrounding bodily material 108 (e.g., cancellous bone, blood, marrow, and soft tissue). The pedicles 102 a, 102 b extend from the vertebral body 104 and surround a vertebral foramen 110. As a point of reference, systems of the present disclosure may be suitable or readily adapted by those of skill in the art for accessing a variety of bone sites. Thus, although the vertebra 100 target site is illustrated, it is to be understood that other bone sites may be accessed and treated by the system 10 (e.g., femur, long bones, ribs, sacrum, etc.).

The first and second cannulas 22 a, 22 b may be employed to form first and second access paths to first and second target site locations 120 a, 120 b. For example, the cannulas 22 a, 22 b are inserted in a bipedicular fashion through respective ones of the pedicles 102 a, 102 b and into the bodily material 108. The cannulas 22 a, 22 b provide access to the corresponding target site 120 a, 120 b at the open distal ends 42 a, 42 b thereof. One or more stylets (not shown) may be employed to assist in forming/accessing the target sites 120 a, 120 b. For example, a series of differently-sized or configured (e.g., sharpened and blunt) stylets may be successively delivered through the respective cannula 22 a, 22 b to form a channel to the target site 120 a, 120 b. Alternatively, or in addition, an outer guide cannula (not shown) may be deployed to form an access path for subsequent insertion of the cannulas 22 a, 22 b.

After the cannulas 22 a, 22 b are positioned within the bodily material 108 at the desired target sites 120 a, 120 b, the cavity-forming devices 20 a, 20 b are assembled to the corresponding cannula 22 a, 22 b. For example, and as shown in greater detail in FIG. 2B, the elongated body 60 a, 60 b is slidably inserted within the corresponding cannula 22 a, 22 b, with the respective working end 62 a, 62 b being distally advanced therethrough. More particularly, with configurations in which the working end 62 a, 62 b is a balloon or other expandable member format, the working end/balloon 62 a, 62 b is transitioned to a contracted state (e.g., deflated) so as to be slidably received through the lumen 44 a, 44 b. The elongated body 60 a, 60 b is positioned relative to the corresponding cannula 22 a, 22 b such that the respective working end/balloon 62 a, 62 b extends distal the corresponding cannula distal end 42 a, 42 b. For example, where the elongated body 60 a, 60 b may include depth markings as described above, the appropriate depth marking will be aligned with the corresponding handle connector 48 a, 48 b (FIG. 1), thereby ensuring that the working end/balloon 62 a, 62 b is fully deployed or extended beyond the corresponding cannula distal end 42 a, 42 b. In other constructions, upon connection of the cannula connector 66 a, 66 b and the corresponding handle connector 48 a, 48 b, the working end/balloon 62 a, 62 b is distal the corresponding distal end 42 a, 42 b and is positioned at the corresponding target site 120 a, 120 b. Placement of the cavity-forming devices 20 a, 20 b may be performed simultaneously or consecutively.

As a point of reference, FIG. 2C provides a lateral view of the vertebral body 104 in which the first working end/balloon 62 a has been deployed (and in the contracted state). As shown, the vertebral body 104 is fractured (referenced generally at 122) and thus exhibits a fractured height H_(F) that is less than a natural or native height H_(N) (designated generally).

With reference to FIG. 3A, the cavity-forming devices 20 a, 20 b are operated to cause the corresponding working ends/balloons 62 a, 62 b to form first and second cavities or voids 124 a, 124 b, respectively, in the bodily material 108. For example, the working ends/balloons 62 a, 62 b may be expanded (e.g., inflated) substantially simultaneously. Alternatively, with embodiments in which a single inflation source 68 a or 68 b (FIG. 1) is provided, the first working end/balloon 62 a is inflated and then sealed in the expanded or inflated state. The inflation source 68 a or 68 b is then fluidly connected to the second working end/balloon 62 b and operated to cause expansion thereof. Following expansion of the working ends/balloon 62 a, 62 b, the expanded working ends 62 a, 62 b are both supporting the vertebral body 108. In this regard, and as best illustrated in FIG. 3B, expansion of the working ends/balloons 62 a, 62 b not only forms the cavities 124 a, 124 b, but also restores or enhances a height of the fractured vertebral body 104. More particularly, a restored height H_(R) is established that beneficially approximates the natural height H_(N). The restored height H_(R) may be the same as, slightly less than, or slightly greater than, the natural height H_(N) (FIG. 2C); in any event, the restored height H_(R) will be greater than the fractured height H_(F) (FIG. 2C).

Returning to FIG. 3A, the second cavity-forming device 20 b is then operated to transition the second working end/balloon 62 b from the expanded state to the contracted state (e.g., the second balloon 62 b is deflated). In the contracted state of the second working end/balloon 62 b, the second cavity-forming device 20 b may be removed from the second cannula 22 b.

Other embodiments of a system and method for bone augmentation are described with reference to FIGS. 4A-4H. A system 410 is illustrated in FIG. 4A that may be similar or identical in most respects to the system 10 described above, and corresponding reference numbers should be understood as analogous. Those of skill in the art will appreciate that system components described above with reference to FIGS. 1-3B and in the various incorporated references may be used with the embodiments described below within the scope of the present disclosure. The system includes an access cannula 422 (preferably generally straightline in configuration), which is shown as engaged into a cancellous bone-including region 508 (that may also include marrow and other body material as noted above with reference to FIGS. 2A-3B) of a vertebra 500 via a vertebral pedicle 502 thereof. The distal end 442 of the access cannula 422 has been directed near a target region/site 520 that is generally central within the bone region 508. A portion of the bone region 508 may be at least partially defined by a cortical rim 506 forming a boundary of the anterior vertebral body 504.

The target site 520 may be identified by a physician preparing for a vertebroplasty procedure. Identification of the target site may include generally determining a central location in the cancellous bone portion of the vertebra 500 that will substantially or at least generally support height-restoration and/or structural augmentation that preferably is at least generally symmetrical with respect to the vertebra and particularly with respect to damaged portion(s) thereof. Generally, the target site may be approximately centered within the bone structure. However, the target site is defined more generally as a pre-determined location within a bone structure that may be determined by treating personnel to provide for symmetrical application of force to treat a bone.

As shown in FIG. 4B, a stylet 470 may be directed through the access cannula 422. The stylet 470 snugly but slidably extends through an overlying delivery tube 414 that preferably is made a flexible polymer having some columnar strength (e.g., polypropylene, PEEK) that will maintain a patent longitudinal lumen upon withdrawal therefrom of the stylet 470. In some embodiments, the delivery tube may include a metal needle with a distal curved length and a distal terminus end opening through which the expandable member is deployed where the metal needle curve and the stylet curve are about the same when unconstrained and are constrained to a generally straightline orientation when constrained during passage through the access cannula. In some embodiments, the delivery tube may include a metal needle with a distal curved length and a distal-most straight length open at its distal terminus and configured to allow an expandable member to be deployed therefrom without significantly curving the expandable member during its deployment. The delivery tube 414 may include at least one radio-opaque marker (e.g., near its distal end) and/or one or more visual indicia near its proximal end providing for user-observation regarding its distal end position relative to the access cannula of the system. The at least one radio-opaque marker includes that the delivery tube may itself be partially or wholly radiopaque. For example, in certain preferred embodiments, a PEEK (or other polymer) delivery tube 414 may be extruded with Barium in it, such that some or all of the entire tube is radiopaque, obviating the need for other radio-opaque indicia.

The stylet 470 preferably is constructed including a memory metal material having a pre-set curve near its distal end. In this manner, the stylet 470 can be deflected to a generally straight orientation while it is being directed through the access cannula 422. The stylet and the delivery tube have sufficient length to extend through and be operable beyond the distal end 442 of the access cannula. Thus, as shown in FIG. 4B, in the time and space that the stylet 470 is advanced out of the distal end 442 of the access cannula 422, its pre-set curve is re-asserted such that the stylet 470 and overlying delivery tube 414 curve into the target region 520. The pre-set curve of the stylet 470 may be offset from its distal end sufficiently to provide a generally straightline portion of the stylet distal of its pre-set curve. A proximal-end structure of the stylet 470 may include indicia 471 showing the direction of curvature of the pre-set curve (FIG. 4C).

In certain embodiments, a system may include a plurality of stylets, each having a different pre-set curve. In this manner, a physician may determine a desirable stylet curvature to reach the target region and select an appropriate stylet. Each stylet may be individually packaged and clearly marked with size and/or curvature, as well as providing other visual indicia of properties of interest to a physician. In use, the physician may determine a desired curvature path between the distal end 442 of the access cannula and the approximate center of the target site (e.g., in the middle of the pre-determined location, which may or may not be generally centered within a bone portion), select a guide stylet including a distal preset curve corresponding to said curvature path from a plurality of guide stylets having different preset curvatures, and insert the selected stylet through the delivery tube before directing the assembled stylet and overlying tube to the target site.

As shown in FIG. 4C, the stylet 470 may be withdrawn from the delivery tube 414 (which is shown as slightly retracted from its furthest extension point) after having created a generally tubular path or void 521 in the material 508 in the target region 520. Thereafter, as shown in FIG. 4D, a cavity-forming device, which may include a working end embodied as—for example—a distal balloon 462, may be directed into the path 521 formed by the stylet 470. A wire or other support structure (not shown) may be provided in the cavity-forming device end 462 to enhance its trackability and pushability through/into the path 521. As a point of reference, FIG. 4E provides a lateral view of the vertebral body 504 wherein the working end/balloon 462 has been deployed (and is still in a contracted state). As shown, the vertebral body 504 being treated is anteriorly fractured (referenced generally at 522) and thus exhibits a fractured height H_(F) that is less than a natural or native height H_(N) (designated generally).

In one preferred embodiment of a method, the delivery tube 414 may be extended all the way to the end of the cavity/void formed with the stylet 470. Thereafter, the cavity-forming device may be extended through the delivery tube 414 until its working end/balloon 462 contacts the bone at the distal end thereof. This may protect, e.g., a balloon or other distal expandable member of the cavity forming device from external damage during introductory movement and provide for its placement in a desired location and orientation. Thereafter, the delivery tube 414 may be withdrawn sufficiently to allow cavity-forming expansion of the working end/balloon 462 as described below. Those of skill in the art will appreciate that one or more of the cavity-forming device, working end/balloon 462 thereof, and the delivery tube may include visual indicia (e.g., markings on the user-held end, radio-opaque indicia at or near the distal end) that enable a user to determine the relative positions of those components to perform a method as described. In this or other embodiments, the inner diameter of the delivery tube 414 and/or the external surface(s) of the cavity forming device(s) may be lubriciously coated (e.g., with silicone, PTFE, and/or another lubricious material).

With reference to FIG. 4F, the cavity-forming device may be operated to cause its corresponding working end/balloon 462 to form a (preferably approximately, generally, or substantially centered) cavity/void in the body material 508. For example, the working end/balloon 462 may be expanded (e.g., inflated). As best illustrated in FIG. 4G, expansion of the working end/balloon 462 not only forms the cavity, but may also restore or enhance a height of the fractured vertebral body 504. More particularly, a restored height H_(R) is established that may beneficially approximate the natural height H_(N). Such a restored height H_(R) may be the same as, slightly less than, or slightly greater than, the natural height H_(N) (FIG. 4E); in any event, any restored height H_(R) will be greater than the fractured height H_(F) (FIG. 4E). If desired for fluoroscopic visualization, radio-opaque contrast material may be provided into the cavity, internal to or external of the expandable member. Transpedicular access for kyphoplasty at a target site approximately centered in the cancellous bone may not be easily achievable without the curved stylet approach of the present disclosure. The limits of patient anatomy, the desirability of minimizing procedure time (for the sake of, e.g., cost and patient health), and the desirability of minimizing patient recovery time all provide for advantages of the present methods and systems.

Thereafter, the expandable member's working end/balloon 462 may be withdrawn. Then, as shown in FIG. 4H, curable material 530 may be delivered into the cavity via the delivery tube 414. In this or other embodiments, the curable material may delivered in a more targeted manner via a curved delivery cannula directed though the access cannula into the cavity. In such an embodiment, the delivery tube 414 may be removed as an intermediate step before introducing the curved delivery cannula. Methods and devices for use in introducing curable material via a curved access cannula in a manner useful within the presently disclosed systems and methods are disclosed in U.S. Pat. Nos. 7,713,273; 7,799,035, and 8,128,633, as well as U.S. Pat. App. Publ. No. 2010/0087828, each of which is incorporated herein by reference in its entirety. It should be understood and appreciated that the “delivery cannula” described therein may include a pre-set curve with structure and function described herein in reference to a “stylet.” As such the term “stylet” as used herein is defined to include a delivery cannula that has an internal lumen dimensioned and oriented for delivering curable material. This definition may therefore, in some embodiments, provide a stylet that is embodied as a delivery cannula, while—in other embodiments—provide a stylet separate from a delivery cannula.

Stated differently, a delivery cannula may be provided with temperature-dependent multi-curve structure and function. This cannula may further include an overlying delivery tube 414 and be operated in the manner described above for a stylet, except that the curable material may be introduced through the delivery cannula (e.g., after it is withdrawn; the expandable member is introduced, activated, and withdrawn; then the delivery cannula—potentially pre-loaded with curable material—is reintroduced).

In some embodiments, a delivery cannula may include a closed distal end terminus and a side-facing opening near the terminus, where the opening is oriented along an outside surface of the curved portion of the delivery cannula near its closed distal end terminus. It may also include proximal-end indicia that show the direction of distal cannula curvature. The curvature of the delivery cannula may be configured to correspond to the pre-set curve of the stylet 470. In some embodiments, the delivery cannula may be pre-loaded with curable material before the delivery cannula is directed through the guide cannula, in order to decrease procedure time and reduce the likelihood of a bolus during introduction of the curable material.

Those of skill in the art will appreciate that embodiments not expressly illustrated herein may be practiced within the scope of the claims, including that features described herein for different embodiments may be combined with each other and/or with currently-known or future-developed technologies while remaining within the scope of the claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting. And, it should be understood that the following claims, including all equivalents, are intended to define the spirit and scope of this invention. Furthermore, the advantages described above are not necessarily the only advantages of the invention, and it is not necessarily expected that all of the described advantages will be achieved with every embodiment. 

We claim:
 1. A system configured for stabilizing a bone structure of a patient, the system comprising: an access cannula configured for penetrating into a bone structure; a guide stylet assembly that comprises a stylet including memory metal and incorporating a distal pre-set curve; and an overlying delivery tube through which the stylet snugly and slidably extends, where the stylet and the delivery tube have sufficient length to extend through and be operable beyond the distal end of the access cannula, and where the pre-set curve is held generally longitudinally straight when the stylet is constrained by the access cannula; an expandable member configured for passage through and deployment outside a distal end of the overlying delivery tube; and proximal end indicia showing the direction of curvature of the stylet's pre-set curve and indicating when a distal end terminus of the stylet is aligned with and ready to exit the distal end of the delivery tube.
 2. The system of claim 1, where the expandable member is embodied as a fluid-inflatable balloon configured to create a cavity by displacing cancellous bone.
 3. The system of claim 1, wherein the stylet comprises_a curved delivery cannula configured for passage through the access cannula. 